A special provision is made for pointers to member
functions. Though they are not function objects, Boost.Function
will adapt them internally to function objects. This requires
that a pointer to member function of the form R
(X::*mf)(Arg1, Arg2, ..., ArgN)
cv-quals be adapted to a
function object with the following function call operator
overloads:

A function object f of
type F is
stateless if it is a function pointer or if
boost::is_stateless<T>
is true. The construction of or copy to a Boost.Function object
from a stateless function object will not cause exceptions to be
thrown and will not allocate any storage.